1. Field of the Invention
The present invention relates generally to a terminal connector or connector assembly for connection to an electrochemical cell. More particularly, the present invention relates in one embodiment to a terminal connector for attaining a simple, reliable connection of a device to a high capacity, high energy density cell used in implantable medical devices. The terminal connector connects to the cell's terminal assembly disposed on the exterior of the cell. That way, the terminal assembly occupies very little of the internal volume of the cell.
2. Description of Related Art
A case-grounded implantable electrochemical cell most commonly provides two terminals of opposed polarity for connection of the cell to a device to be powered. One terminal extends from a glass-to-metal seal, and the other terminal extends from the case. Prior art terminals are disadvantageous in that one of the terminals typically protrudes inwardly into the cell casing, thereby reducing the casing volume available for containing the active cell materials. The use of prior art terminals thus results in a reduction of the overall cell volumetric efficiency. Additionally, the connection of the cell terminals to the device to be powered is typically accomplished by soldering, welding, or wire-bonding the cell terminals to the device.
For both the central terminal pin extending from the glass-to-metal seal, and the case grounding terminal that is welded or otherwise joined to the cell casing, each is comprised of a fine wire extending outwardly from the casing. These wires are fragile and are thus susceptible to displacement and fracture by bending during cell handling. Additionally, it is difficult to position the terminal wires precisely and to maintain such positioning in the event they are to be matched with specific corresponding terminals of the device to be powered by the cell when making connection with such a device. The terminal wires are easily bent and misaligned during handling of the cell prior to connection to the device.
Heretofore, a number of patents and publications have disclosed cells including terminal connections to powered devices. For example, U.S. Pat. No. 5,250,373 to Muffoletto et al., which is assigned to the assignee of the present invention and incorporated herein by reference, describes an electrochemical cell including a central lead that is fixed relative to a lid by a generally cylindrical ferrule element, which is fitted at one end to an opening in the lid and secured to the lid by welding. The space between the lead and the ferrule is filled by a glass seal that extends along the major portion of the length of the ferrule. This glass-to-metal seal insulates the lead electrically from the lid and the cell casing, and seals the lead so that no egress or ingress of gases or liquids into or out of the casing can occur. The entire glass-to-metal seal is disposed beneath the lid on the interior of the cell casing. This assembly thus occupies space within the cell casing that could be more advantageously used for active materials, which would increase the cell's volumetric efficiency and capacity.
Additionally, U.S. Pat. No. 6,004,692 to Muffoletto et al., which is assigned to the assignee of the present invention and incorporated herein by reference, describes an electrochemical cell including an electrode assembly constructed of a serpentine electrode with interleaved counter electrode plates. The electrochemical cell disclosed therein also includes a glass-to-metal seal assembly similar to that disclosed in the aforementioned U.S. Pat. No. 5,250,373 to Muffoletto et al., wherein the lead is connected to the interleaved cathode plates by a cathode bridge. These are only two examples of many conventionally constructed electrochemical cells having the glass-to-metal seal assembly disposed beneath the lid on the interior of the casing, thus using space within the cell that could be more advantageously used for active materials.